I figured I would make a thread for my new engine prototype instead of cluttering up the FS26 thread, so here goes!
I named the thread (and for now, the engine) the "Thump-8" because I'm not sure what the final displacement will be. The initial prototype is looking like it'll be about .39ci, but that number can easily change with slight variances in bore and stroke without changing the overall design, depending on how much power and RPM I can wring out of it.
The goal of this design is to end up with a 4 stroke engine that bolts directly into any place a current .21 two-stroke fits, and is able to use the same (or at least very similar) gearing and clutch hardware. The reality may be slightly different than that, but that's the point - to find out if it's possible. Nobody has ever attempted this before (that I know of). It will need to be compact, VERY high-revving and if I can manage, I would like it to not require a cooling fan... Pie-in-the-sky stuff for sure, but the project should be at least lots of fun.
I haven't made metal chips fly yet, but I have discovered Google SketchUp, which allows me to model my engine in 3 dimensions. It's pretty easy to use, and I've already modeled a good portion of the valve system. As I continue to learn how to use the program, I can see it's going to benefit the design and engineering process in a big way. Much better than drawing in 2 dimensions and just trying to imagine how it would work in 3-D.
Tonight, I get to pick up my prototype piston, ring, wristpin, and sleeve. Once that stuff gets digitized, I'll have something concrete to base some dimensions off of.